Mucopolysaccharidosis type VII (MPS VII, ft glucuronidase deficiency) has been described in association with nonimmune hydrops fetalis. Three consecutive pregnancies in an itinerant family, which resulted in stillbirths caused by non-immune hydrops are described. The parents were closely related and there was a strong family history of storage disorders. The main clue to the diagnosis, however, came from the presence of pronounced foamy cytoplasmic change in the villous Hofbauer celis of the placenta. This raised the possibility of an inherited metabolic storage disorder. The parents were subsequently shown to have f glucuronidase activities in the heterozygous range in leucocytes and fibroblasts which suggested that the nonimmune hydrops was caused by ft glucuronidase deficiency.
A 2.5‐year‐old girl who presented with abdominal distension, hepatomegaly, coarse fades, hirsutism and contraction deformities was investigated for mucopolysaccharidoses. Urinary excretion showed increased total glycosaminoglycans (105 mg/mmol creatinine; normal for age 9–20 mg/mmol) with marked increases of dermatan and heparan sulphates. A number of lysosomal enzyme activities were measured on leucocytes, serum and cultured fibroblasts. Normal or high activities were found for a‐iduronidase, N‐acetylgalactosamine‐6‐sulphatase, β‐galactosidase, arylsulphatase B and /J‐glucuronidase. However a marked deficiency ofiduronate sulphate sulphatase activity was observed, consistent with a diagnosis of Hunter's disease. Activities were reduced to less than 2% of mean control values in the patient's leucocytes, serum and cultured fibroblasts. Normal activities were measured in samples from the father and younger sister but a partial deficiency (43% of control serum) was found in the mother. Chromosome studies on the patient revealed a partial deletion of the long arm of one X‐chromosome, most probably of band Xq25, which was not inherited from either parent. Studies using BrdU indicated that the deleted X chromosome was consistently late replicating, and as a result the Hunter gene was fully expressed on the other X chromosome.
A low arylsulphatase A activity was noted in the leukocytes and cultured skin fibroblasts of a child without any other symptoms of metachromatic leukodystrophy. Although the mother had a level of arylsulphatase A commensurate with heterozygosity for the classical metachromatic leukodystrophy gene, the father had a variant gene giving an unusually low in vitro level of this enzyme. In combination (the proband), these two genes gave rise to a very low in vitro activity without any apparent disease. In screening for metachromatic leukodystrophy, a low arylsulphatase A level is not necessarily indicative of this disease, if a clinically normal parent shows an unusually low Ievel of this enzyme.
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